Accretion of Low Angular Momentum Material onto Black Holes: Radiation Properties of Axisymmetric MHD Flows

TL;DR

This paper investigates the radiation properties of axisymmetric MHD accretion flows onto black holes, revealing that spectral variability does not always directly correspond to accretion state changes, with implications for understanding underluminous galactic centers.

Contribution

It combines MHD simulations with Monte Carlo spectral calculations to analyze the relationship between accretion flow variability and emitted spectra.

Findings

Spectral variability is not always correlated with accretion state.

No one-to-one correspondence between accretion flow and spectrum.

Spectra can remain stable despite flow variability.

Abstract

Numerical simulations of MHD accretion flows in the vicinity of a supermasssive black hole provide important insights to the problem of why and how systems -- such as the Galactic Center -- are underluminous and variable. To access applicability of such flows to real objects, we examine the dynamical MHD studies with computations of the time dependent radiation spectra predicted by the simulations. We apply Monte Carlo methods to calculate spectra predicted by the time-dependent model of an axisymmetic MHD flow accreting onto a black hole presented by Proga and Begelman. Our calculations show that variability in an accretion flow is not always reflected in the corresponding spectra, at least not in all wavelengths. We find no one-to-one correspondence between the accretion state and the predicted spectrum